[Nicardipine inhibits phosphate reabsorption regardless of glomerular filtration rate in hypertensive surgical patients].

The author investigated the mechanism of diuretic effect of a calcium entry blocker of dihydropyridine derivative, nicardipine, in comparison with furosemide given during surgical interventions on 13 hypertensive patients. In another group of 16 surgical patients, a bolus of furosemide 10 mg is given for a control. In hypertensive patients, intravenous nicardipine in doses of 1 to 2 micrograms.kg-1.min-1 produced normotensive state during surgery accompanied by significant diuresis. The extent of diuresis produced by the two agents, nicardipine and furosemide, was similar in urine volume and sodium excretion rate. On the contrary, the fractional excretion of PO4 (FEP) increased from 9.4 +/- 5.5% to 29.8 +/- 10.4% only after nicardipine. Plasma levels of electrolytes (Na, K, Ca, PO4) and parathyroid hormone showed no change during the study in the two groups. Nicardipine induced diuresis and phosphaturia in all hypertensive surgical patients regardless of the levels of creatinine clearance, plasma PO4 and parathyroid hormone. As organic phosphate reabsorption occurs largely in the proximal tubule, increased phosphaturia suggests that the proximal tubule is activated by nicardipine.